Which of the following is an example of a closed system? a) the earth system b) the ocean c) an ecosystem d) a biome e) material or energy that is able to move in or out of a system

they deliver oxygen to the blood

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]